Yet another 16-color CGA makeover: Keen 5

After giving Keen 4's CGA version a 16-color composite overhaul, I
figured I'd have a go at the next episode, since the code has nearly
everything in common with Keen 4, and the composite enhancements
detailed in my previous post could be applied without too many
essential changes (other than different offsets/addresses, of course).
Let's strap this one to the rack then:

As before, the distribution is a runtime in-memory patch (using
CK5PATCH) and you'll need the original KEEN5 CGA files (v1.4 Apogee
release). If you're hardcore enough to go the real hardware route,
you'll also need DOS 3.3+, a true blue IBM CGA card (early/'old'-style
is best), and a composite monitor/TV.

Naturally, the graphics data for the game had to be completely reworked
here too. Compared to episode 4 this was interestingly different: Keen
4 has a mostly organic-looking, earthy style to its environments, with
plenty of curved or irregular shapes and large details; Keen 5 goes for
the 'tech' look, with straighter lines and lots of small elaborate
mechanistic decor. Given the limitations of composite video, both were
artistically challenging to rework, though in rather different ways.

The only real 'new' piece of code this time is the palette animation for
the game over screen; the EGA version messes with the galaxy colors
before the particle explosion (which, BTW, is a slideshow on a real
XT!), but the vanilla CGA version settles for a boring static image.
The CGA code didn't helpfully hold my hand this time either, since I had
no stubs / calls to blank leftover functions to work with, like I had
with the fades.

In the end I rolled my own routine, which only kinda-sorta mimics its
EGA counterpart visually (EGA can alter individual color registers,
while composite CGA in mode 6 may only modify the foreground color,
which in turn changes the entire set of 16 artifact colors). On the
other hand, I guess it's pretty neat that these color changes can still
be tailored to make *parts* of a particular image disappear/reappear,
instead of having a uniform fade.